docs: def get_classes(module_label, classnames):
      """ Imports a set of classes from a given module.
  
      Usage::
  
          get_classes('forum.models', ['Forum', 'ForumReadTrack', ])
  
      """
      app_label = module_label.split('.')[0]
  
      app_module_path = _get_app_module_path(module_label)
      if not app_module_path:
          raise AppNotFoundError('No app found matching \'{}\''.format(module_label))
  
      # Determines the full module path by appending the module label
      # to the base package path of the considered application.
      module_path = app_module_path
      if '.' in app_module_path:
          base_package = app_module_path.rsplit('.' + app_label, 1)[0]
          module_path = '{}.{}'.format(base_package, module_label)
  
      # Try to import this module from the related app that is specified
      # in the Django settings.
      local_imported_module = _import_module(module_path, classnames)
  
      # If the module we tried to import is not located inside the machina
      # vanilla apps, try to import it from the corresponding machina app.
      machina_imported_module = None
      if not app_module_path.startswith('machina.apps'):
          machina_imported_module = _import_module(
              '{}.{}'.format('machina.apps', module_label), classnames,
          )
  
      if local_imported_module is None and machina_imported_module is None:
          raise AppNotFoundError('Error importing \'{}\''.format(module_path))
  
      # Any local module is prioritized over the corresponding machina module
      imported_modules = [
          m for m in (local_imported_module, machina_imported_module) if m is not None
      ]
      return _pick_up_classes(imported_modules, classnames)